Using a lysimetric station to determine the irrigation water requirements for chufa crop (Cyperus esculentus var. sativus)

Abstract

Chufa, also known as tigernut, is a typical irrigated crop in Valencia, Spain, where it is traditionally cultivated for its tubers. Its cultivation uses large amounts of water, in the order of 10,000 m3 ha(‑1) year‑1. During the last years, the research team in which this study has been developed, has carried out several studies leading to improve the irrigation water use efficiency in chufa. Although these improvements are considerable, they are not definitive, as the water requirements of the crop are still unknown. To know these needs, it would be recommended to determine the crop evapotranspiration (ETc). The experiment was carried out on an experimental plot of the Universitat Politecnica de Valencia, included in the traditional cultivation area. This plot includes a lysimetric station (Smart Field Lysimeter) which allows determining the daily ETc. In addition, the plot is equipped with a meteorological station, which provides the necessary parameters for the determination of the daily reference crop evapotranspiration (ETo) through the FAO-56 Penman-Monteith method. Relating the values of ETc and ETo, the crop coefficient (Kc) values corresponding to the different growth stages, has been estimated from the data obtained during the crop cycle. Considering the crop development, the length of the four growth stages were considered as 21, 76, 43 and 29 days for initial, development, mid-season and late season stages, respectively. The single Kc values for the initial, mean and end of the late season stages were established as 0.25, 1.43 and 0.75, respectively. The use of these Kc values will allow adjusting irrigation water doses to water requirements, thus reducing the volume of water applied and improving the irrigation application efficiencies in chufa crop.